Combined Sizing and Aircraft Evaluation of an Electrically Assisted Propulsion System

The design of hybrid electric propulsion (HEP) systems involves multiple sizing requirements and operating conditions that affect aircraft performance. Assessing their overall potential requires the coupled consideration of hybridization, battery technology, mission utilization and operational constraints. Therefore, an integrated methodology combining HEP sizing with simplified aircraft design and performance methods is presented. A parallel HEP concept with an electrically assisted compressor is investigated for a 50 PAX regional aircraft and a 19 PAX helicopter, considering an Entry-Into-Service (EIS) in Y2035+. To enable operation without electrical assistance, gas turbine oversizing is applied. This comes with mass and efficiency penalties but significantly expands the operational hybridization range. At a battery system specific energy of 500 Wh/kg, the regional aircraft achieves a 1% block fuel reduction on the design mission (400 nmi), compared with a 22% reduction on the shorter typical mission (150 nmi) through increased battery utilization. For the helicopter, block fuel increases by 11% on the design mission, but decreases by 10% on the typical mission. The results demonstrate that aircraft utilization is a key factor for the sizing and assessment of parallel HEP systems.